Leptin administration does not prevent the bone mineral metabolism changes induced by weight loss

The objective was to examine the effects of weight loss and leptin administration following weight loss on calciotropic hormones and bone turnover. This was a prospective, single-blinded study of 12 subjects (8 women, 4 men; 2 nonobese, 10 obese; age range, 19-46 years) who were studied on an inpatient basis while maintaining their usual weight [Wtinitial] and during maintenance of 10% weight loss while receiving twice-daily injections of either a placebo [Wt−10%P] or replacement doses of leptin [Wt−10%L]. The main outcome measures were markers of bone formation (bone alkaline phosphatase and procollagen type 1 amino terminal propeptide) and resorption (N-telopeptide) as well as parathyroid hormone, calcium, and 25-hydroxy vitamin D measured from fasting morning serum. As expected, serum leptin declined with weight loss. Bone alkaline phosphatase decreased by 12.3% ± 3.9% between Wtinitial and Wt−10%P and remained suppressed after leptin administration (both P < .01 compared with baseline). N-telopeptides increased by 37.2% ± 11.3% from Wtinitial to Wt−10%L (P < .01). Procollagen type 1 amino terminal propeptide, parathyroid hormone, calcium, and 25-hydroxy vitamin D did not change. These results suggest that both decreased bone formation and increased bone resorption underlie bone loss associated with weight loss. Leptin administration did not prevent the uncoupling of bone remodeling that accompanies weight loss.